expectant mother is told she

is about to have twins, her initial reaction is shock. Yet this is not an uncommon occurrence, as one in every 86 pregnancies is a multiple birth. There may be more twins in the next few generations, since advances in medicine are saving more premature twins, some of whom will become the parents and grandparents of other twins. After the mother has had her babies, she will have many concerns and questions about twins. She may find some solutions through a local Mothers of Twins Club, but many questions will be directed to her pediatrician. Q. What are my chances of having twins


Queries That

A. When a woman has had twins once, her chances of having twins again are three to ten times greater .7 Fraternal twins are three times more likely to be born to mothers in the 35 to 40 age group than to mothers who are 20 to 24 years old. With identical twins, the incidence does not seem to be significantly affected by the mother’s age. The highest prevalence of twins is among the Yorubas of Nigeria, in whom twins occur in one of every 22 pregnancies. The opposite is true in Japan, where twins occur only once in 254 births. In the United States, twins occur once in 110 births in the white population, and somewhat more frequently in the black population. Geographic differences also exist in the incidence of twins. In Kentucky, for example, twin births occur twice as frequently (1 in 67 births) as in Nevada ( in 124 births). Q. Would I be likely to have triplets or quadruplets next time? A. Probably not. If we take one in 80 births to be the worldwide incidence of twins, then the incidence of triplets is 80 x 80, or 1 chance in 6,400. The chances of having quadruplets are 1 in 512,000 (one

Mothers of Twins Put to Their Doctors





Associate Professor of Psychiatry, Department of the Medical School, and Chief of Clinical Services at the Institute for the Study of Mental Retardation and Related Disabilities, University of Michigan, 130 S. First Street, Ann Arbor, Mich. 48108. *

University of Michigan



in 80 x 80 x 80). Multiple births do tend to in families, although we do not know the exact way that a familial tendency to multiple births is inherited. One mother is reported to have given birth to two sets of triplets within eleven months-imagine taking care of six children under one year of age! Probably the world record is in Australia where a woman reportedly had a total of 69 children-four sets of quadruplets, seven sets of triplets, and lfi sets of twins !2 run

When a woman has had twins once, her chances of having twins again are three to ten times greater.

Q. What is the real difference between identical and fraternal twins? A. Identical twins are produced from the same fertilized egg which, for some reason, divides and produces two individuals with exactly the same genetic makeup. Fraternal twins are produced by two separate eggs fertilized by two different sperm. Thus, the two individuals are genetically no more alike than any two siblings in that family. In fact, in a famous case in Chicago in 1938, two men claimed paternity to a set of twins; blood-typing proved that each was the father of one twin 17 Q. Are fraternal or identical twins more common, and can I tell which type I have? A. Fraternal twins are the more frequent. One common-sense formula for estimating the fraternal twins in a population is to count the mixed pairs (boy-girl) and multiply that number by two. Then, subtracting these fraternal from the total group of twins would give the identical twins. It is estimated that, for 100 twins in the United States among the white population, 65 are fraternal and 35 are identical. Among the United States black population, for every 100 twins, 71 are fraternal and 29 are identical.’7 We used to think special tests, such as blood typing, were essential to decide whether twins are fraternal or identical. A recent study showed, however, the mothers perception of whether the twins were identi-

cal proved time.1




98 per


of the

Q. Are most twins premature? And do they have problems because of this? A. About 60 per


of twins



by weight ~i.e., weigh less than 5 pounds, 8 ounces). Occasionally, very large ture

twins have been born, with some even hava combined weight of over 18 pounds. Premature twins are susceptible to all the problems that other prematures have. For example, during childhood, most twins are shorter and weigh less than average singleborns. Generally speaking, however, premature twins do better than premature singleborns. Q. I have heard that twins are not so bright as single children. Is this true? A. Some studies measuring 1. Q. scores on children have shown that, on an average, twins test out five to nine points below the I.Q. scores of single children. Several factors have to be kept in mind when we say this. First, 1. Q. scores are not always a clear reflection of a child’s intellectual potential. Secondly, the factor that seems to influence 1. Q. scores the most is the socioeconomic level of the family. In fact, were we to compare a sample of twins from a middle- or upper-socioeconomic class with a sample of single children from a low-socioeconomic class, the twins would probably score higher than the single children.~ 3 third, such data


About 60 per cent of twins



by weight ... based on averages and say very little about a given twin pair. In summary, one must be careful not to generalize here. Q. Do twins show similar scores in I. Q. tests? A. Again, remember, we are dealing with averages, and this may or may not apply to your twins. Identical twins seem to show the least differences in 1. Q. scores, being about five points apart. Fraternal twins show a greater variation, about 8.5 points apart. Siblings in the same families have a 7range of about 10 to 15 points in difference.7 are


Q. I have heard about many studies on mental illness done on twins-is this because there is more mental illness in twins? A. No studies do not indicate that there is more mental illness in twins. The reason for the many studies on twins is to try to assess how great a role heredity plays in mental illness. This is approached by comparing the incidence of mental illness in fraternal twins vs. identical twins. Other studies have tried to find why one identical twin may show mental illness whereas the other does not. Q. Have reasons been found why one of a pair of identical twins will show mental illness? A. Generally, the second born or smaller twin seems the most vulnerable. It has been postulated that, with the smaller twin, both parental overprotection and the physiologic effects of low weight may be responsible.4 Q. What about stressing the differences between twins, i.e., should they be dressed alike or different; should they be in the same classrooms or separated? A. A great deal depends on the twin pair. If they are prone to stay together to the extent of excluding other friends and seem to have problems developing their individuality, then their differences should be emphasized during their rearing. As for dressing them alike, this may be fun sometimes, but can you imagine doing this all the time? Each time one twin is dirty, both will have to be changed! Classrooms are tricky. Somtimes it is best to have twins in separate classrooms, so that they make friends separately, and usually this tends to decrease competition in schoolwork. Some twins, in contrast, seem to be less competitive when they are in the same classroom. Apparently, knowing how the other twin is doing may diminish some anxiety that the other twin is doing superwell (or having much more fun), and brings competition within a realistic range. Usually, unless the twins are obviously too dependent on each other, it is sensible to ask the twins themselves whether they would like to be together or in different classrooms. Q. Since twins are usually close to each 626

other emotionally, how much difficulty do they have in forming other relationships? A. This is not a problem with most twins. In a study of twins done in a nursery school, many initially played only with each other, but the longer they stayed in the school, the more they played with other children .4 Interestingly, in adolescence, some studies have shown that twins are generally more popular than singletons.~ In a study of adult twins, no correlation was apparent between the degree of closeness of the twins and whether they were married or not. Thus, except in extreme cases, most twins can be quite close to each other without significantly interfering with other relationships.5 Q. How about the older children in the family? Is it difficult for them to accept twins? A. I am glad you brought this up. It is very easy to forget the impact of two babies upon a family. Usually, both parents are busy with the two new babies, and any guests who come fuss over them. Hence, an older child may feel left out unless special attention is also devoted to him. I know of one family where the parents felt they had prepared an older child for twins, and then had him actively participate in their care. However, a week after the twins were brought home, the little boy asked-&dquo;I still have a question about twins-where is the other one of me?&dquo; References 1. Cohen, Donald, al Separating identical from et .: fraternal twins. Arch. Gen. Psychiatr. 29: 465,


Hicks, Clifford: Why are twins so special? Today’s Health, December, 1963, p. 19. 3. Mittler, Peter: The Study of Twins. Middlesex, England, Penguin Books, Ltd., 1971. 4. Paluszny, M., and Gibson, R.: Twin interaction in a 2.

normal nursery school. Am.

J. Psychiatr.

3, 1974. 5. Paluszny, M., and Beit-Hallahmi, B.: An



of monozygotic twin relationships by the semantic differential. Arch. Gen. Psychiatr. 31: 110, 1974. .: Family studies with identical 6. Pollin, William, et al twins discordant for schizophrenia. Psychiatry 28: 60, 1965. 7. Scheinfeld, Amram: Twins and Supertwins. New York, J. B. Lippincott Co., 1967.

Queries that mothers of twins put to their doctors.

COUNSELING WHEN an expectant mother is told she is about to have twins, her initial reaction is shock. Yet this is not an uncommon occurrence, as...
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